Fan mounting in combo

Anybody have pic showing the proper mounting location of the fan in a Mark IV widebody, or any Mark?

If they are like the short chassis combo cabs the fan is mounted to the side and rear panel about 6-8 inches up from the bottom
In order to see the fans' location more clearly you have to take the front grille off and remove the speaker.
Then look/ reach through the hole where the speaker was to see/ get at the fan (and the brackets that hold it to the rear & side panels).

In any case maybe this gives you an idea of where the fan is mounted.....

Thanks.

If you google "mesa boogie mark IV back" and choose the images tab you'll see lots of pictures of where the fan goes.

Is a fan absolutely necessary though? I bought my combo used, and it doesn't have a fan. It came from a studio, maybe they removed it.